Semiconductor device having modified profile metal gate

ABSTRACT

A semiconductor device has a semiconductor substrate with a dielectric layer disposed thereon. A trench is defined in the dielectric layer. A metal gate structure is disposed in the trench. The metal gate structure includes a first layer and a second layer disposed on the first layer. The first layer extends to a first height in the trench and the second layer extends to a second height in the trench; the second height is less than the first height.

PRIORITY DATA

The present application is a Continuation Application of U.S. Ser. No.15/614,274 filed Jun. 5, 2017, issuing as U.S. Pat. No. 10,418,456,which is a Continuation Application of U.S. Ser. No. 14/952,733 filedNov. 25, 2015, now U.S. Pat. No. 9,673,292, which is a DivisionalApplication of U.S. Ser. No. 13/745,205, filed Jan. 18, 2013, entitled“SEMICONDUCTOR DEVICE HAVING MODIFIED PROFILE METAL GATE,” now U.S. Pat.No. 9,202,691, each of which is hereby incorporated by reference in itsentirety.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experiencedexponential growth. Technological advances in IC materials and designhave produced generations of ICs where each generation has smaller andmore complex circuits than the previous generation. In the course of ICevolution, functional density (i.e., the number of interconnecteddevices per chip area) has generally increased while geometry size(i.e., the smallest component (or line) that can be created using afabrication process) has decreased. This scaling down process generallyprovides benefits by increasing production efficiency and loweringassociated costs. Such scaling down has also increased the complexity ofprocessing and manufacturing ICs and, for these advances to be realized,similar developments in IC processing and manufacturing are needed.

One advancement implemented as technology nodes shrink, in some ICdesigns, has been the replacement of the typically polysilicon gateelectrode with a metal gate electrode to improve device performance withthe decreased feature sizes. One process of forming a metal gate stackis termed a replacement gate or “gate last” process in which the finalgate stack is fabricated “last,” which allows for reduced number ofsubsequent processes, including high temperature processing that must beperformed after formation of the gate. Such a process uses a dummy gatestack, which is subsequently removed and replaced with a metal gatestack. There are challenges to implementing such features and processesin the scaled down processes however. For example, filing the trenchprovided by the removal of a dummy gate stack encounters an aspect ratiothat is challenging to fill without inducing voiding.

Thus, while the present gate-last processes of forming a metal gate aresuitable in many respects, there may be a desire to improve the methodsand/or devices to reduce the gap-filling issues for example.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isemphasized that, in accordance with the standard practice in theindustry, various features are not drawn to scale. In fact, thedimensions of the various features may be arbitrarily increased orreduced for clarity of discussion.

FIG. 1 is a method of fabricating a semiconductor device according toone embodiment of the present disclosure including a profilemodification process.

FIGS. 2-9 are cross-sectional views of an exemplary semiconductor devicefabricated according to one or more steps of the method 100.

FIG. 10 is a method of fabricating a semiconductor device according toanother embodiment of the present disclosure including a profilemodification process.

FIGS. 11-14 are cross-sectional views of an exemplary semiconductordevice fabricated according to one or more steps of the method 100.

FIGS. 15-20 are cross-sectional views of exemplary semiconductor deviceshaving modified profile gate structures.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof the invention. Specific examples of components and arrangements aredescribed below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Moreover,the formation of a first feature over or on a second feature in thedescription that follows may include embodiments in which the first andsecond features are formed in direct contact, and may also includeembodiments in which additional features may be formed interposing thefirst and second features, such that the first and second features maynot be in direct contact. Various features may be arbitrarily drawn indifferent scales for simplicity and clarity.

Illustrated in FIG. 1 is a method 100 of fabricating a semiconductordevice using a replacement gate (also referred to as gate-last)methodology that includes modifying the profile or shape of at least onelayer that forms a gate structure. The modifying of the profile of atleast one layer of the gate structure may also be referred to asre-shaping the gate structure. The modification of the profile orre-shaping provides an opening for the trench, within which the gatestructure is formed, that may allow for improved gap filling of thetrench. This may provide a benefit, for example, reduction of voidingthat may form in the replacement gate structure due to fillingdifficulties with a high aspect ratio trench. FIGS. 2-9 arecross-sectional views of an embodiment of a semiconductor devicefabricated according to one or more of the steps of the method 100.

It is understood that the method 100 includes steps having features of acomplementary metal-oxide-semiconductor (CMOS) technology process flowand thus, are only described briefly herein. Additional steps may beperformed before, after, and/or during the method 100. Similarly, onemay recognize other portions of a device that may benefit from themethods described herein. It is also understood that parts of thesemiconductor devices of FIGS. 2-9 may be fabricated by complementarymetal-oxide-semiconductor (CMOS) technology process flow, and thus someprocesses are only briefly described herein. Further, these devices mayinclude various other devices and features, such as additionaltransistors, bipolar junction transistors, resistors, capacitors,diodes, fuses, etc., but is simplified for a better understanding of theinventive concepts of the present disclosure. These devices may alsoinclude a plurality of semiconductor devices (e.g., transistors), whichmay be interconnected. The devices may be intermediate devicesfabricated during processing of an integrated circuit, or portionthereof, that may comprise static random access memory (SRAM) and/orother logic circuits, passive components such as resistors, capacitors,and inductors, and active components such as P-channel field effecttransistors (PFET), N-channel FET (NFET), metal-oxide semiconductorfield effect transistors (MOSFET), complementary metal-oxidesemiconductor (CMOS) transistors, bipolar transistors, high voltagetransistors, high frequency transistors, other memory cells, andcombinations thereof.

The method 100 begins at block 102 where a substrate having a dummy gatestructure disposed thereon is provided. The substrate may be a siliconsubstrate. Alternatively, the substrate may comprise another elementarysemiconductor, such as germanium; a compound semiconductor includingsilicon carbide, gallium arsenic, gallium phosphide, indium phosphide,indium arsenide, and/or indium antimonide; an alloy semiconductorincluding SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; orcombinations thereof. In one embodiment, the substrate is asemiconductor on insulator (SOI) substrate.

The dummy gate structure includes at least one sacrificial layer. Thedummy gate structure may include an interface layer (IL), a gatedielectric layer, a dummy gate electrode layer, and/or other suitablelayers. In an embodiment, the IL may include a dielectric material suchas silicon oxide layer (SiO₂) or silicon oxynitride (SiON). The IL maybe formed by chemical oxidation, thermal oxidation, atomic layerdeposition (ALD), CVD, and/or other suitable dielectric. In anembodiment, the gate dielectric layer includes an oxide such as SiO₂. Inother embodiments, the gate dielectric layer may include a low-kdielectric as hafnium oxide (HfO₂), TiO₂, HfZrO, Ta₂O₃, HfSiO₄, ZrO₂,ZrSiO₂, combinations thereof, or other suitable material. The dielectriclayer may be formed by thermal oxidation, atomic layer deposition (ALD)and/or other suitable methods. In an embodiment, the dummy gateelectrode layer includes polysilicon and/or other suitable material. Thedummy gate electrode layer may be formed by CVD, PVD, ALD, othersuitable methods, and/or combinations thereof.

The dummy gate structure can be formed by a procedure includingdepositing, photolithography patterning, and etching processes to formthe stack. As discussed above, a plurality of layers may be formed ordeposited. These layers may then been patterned to form a gate stack.The photolithography patterning processes include photoresist coating(e.g., spin-on coating), soft baking, mask aligning, exposure,post-exposure baking, developing the photoresist, rinsing, drying (e.g.,hard baking), other suitable processes, and/or combinations thereof. Theetching processes include dry etching, wet etching, and/or other etchingmethods (e.g., reactive ion etching).

In embodiments, spacer elements may be formed abutting the sidewalls ofthe dummy gate structure prior to or after the formation of thesource/drain regions (or portions thereof). The spacer elements may beformed by depositing a dielectric material followed by an isotropicetching process, however other embodiments are possible. In anembodiment, the spacer elements include silicon oxide, silicon nitride,and/or other suitable dielectrics. The spacer elements may include aplurality of layers.

The method 100 may also include forming additional features. In oneembodiment, source/drain regions are formed. The source/drain regionsmay include the introduction of suitable dopant types: n-type or p-typedopants. The source/drain regions may include halo or low-dose drain(LDD) implantation, source/drain implantation, source/drain activationand/or other suitable processes. In other embodiments, the source/drainregions may include raised source/drain regions, strained regions,epitaxially grown regions, and/or other suitable techniques.

In an embodiment, a contact etch stop layer (CESL) and an interlayerdielectric (ILD) layer are formed on and around the dummy gatestructure(s). Examples of materials that may be used to form CESLinclude silicon nitride, silicon oxide, silicon oxynitride, and/or othermaterials known in the art. The CESL may be formed by PECVD processand/or other suitable deposition or oxidation processes. The ILD layermay include materials such as, tetraethylorthosilicate (TEOS) oxide,un-doped silicate glass, or doped silicon oxide such asborophosphosilicate glass (BPSG), fused silica glass (FSG),phosphosilicate glass (PSG), boron doped silicon glass (BSG), and/orother suitable dielectric materials. The ILD layer may also be depositedby a PECVD process or other suitable deposition technique.

The method 100 then continues to block 104 where the dummy gatestructure is removed to provide a trench or opening. The removal of thedummy gate structure may include a planarization process used to exposea top surface of the dummy gate structure. The planarization process mayinclude a chemical mechanical planarization (CMP) process. Uponexposure, the dummy gate structure may be removed in whole in or part bysuitable wet and/or dry etching processes. In one embodiment, the gatedielectric is removed. In another embodiment, the gate dielectric iskept and provided in the final gate structure.

Referring to the example of FIG. 2, illustrated is a device 200 having asubstrate 202, an ILD layer 204, a CESL 206, spacer elements 208, and atrench 210. The trench 210 is provided by the removal of a dummy gatestructure (not shown).

The method 100 then continues to block 106 where an interface layer (IL)is formed in the trench. The interface layer may be a gate dielectriclayer such as SiO₂, Al₂O₃, and/or other suitable material. The interfacelayer may be provided by thermal oxidation, chemical oxidation, and/orother suitable process. Referring to the example of FIG. 3, an interfacelayer (IL) 302 is disposed in the trench 210.

The method 100 then proceeds to block 108 where a dielectric layer isformed in the trench. The dielectric layer (and/or the IL) may providethe gate dielectric for the semiconductor device. In one embodiment, thedielectric layer includes a high-k dielectric layer such as hafniumoxide (HfO₂). Alternatively, the high-k dielectric layer may optionallyinclude other high-k dielectrics, such as TiO₂, HfZrO, Ta₂O₃, HfSiO₄,ZrO₂, ZrSiO₂, combinations thereof, or other suitable material. Thedielectric layer may be formed by ALD and/or other suitable methods.Referring to the example of FIG. 4, a dielectric layer 402 is formed onthe substrate. The dielectric layer 402 may be a high-k dielectriclayer.

The method 100 then proceeds to block 110 where a barrier layer isformed on the substrate including in the trench. The barrier layer mayinclude TaN, however other compositions may also be suitable. In oneembodiment, the barrier layer is a composite layer. Referring to theexample of FIG. 5, a barrier layer 502 is disposed on the substrate 202including in the trench 210. In an embodiment, block 110 is omitted.

The method 100 then proceeds to block 112 where a work function metallayer is formed on the substrate including in the trench. A workfunction metal layer included in the gate structure may be an n-type orp-type work function layer. Exemplary p-type work function metalsinclude TiN, TaN, Ru, Mo, Al, WN, ZrSi₂, MoSi₂, TaSi₂, NiSi₂, WN, othersuitable p-type work function materials, or combinations thereof.Exemplary n-type work function metals include Ti, Ag, TaAl, TaAlC,TiAlN, TaC, TaCN, TaSiN, Mn, Zr, other suitable n-type work functionmaterials, or combinations thereof. The work function layer may includea plurality of layers (e.g., be a composite layer). The work functionlayer(s) may be deposited by CVD, PVD, ALD, and/or other suitableprocesses.

Referring to the example of FIG. 6, a work function metal layer 602 isdisposed on the substrate 202 including in the trench 210. The workfunction metal layer 602 is illustrated as a contiguous layer betweenthe two trenches illustrated on the substrate 210; however, otherembodiments are possible. For example, different work function metallayer(s) may be formed depending on the type of device associated withthe gate to be formed in the trench.

In an embodiment, additional layers may be formed in the trench beforeor after those discussed above. In one embodiment, an additional barrierlayer is formed after the work function layer(s).

The method 100 then proceeds to block 114 where a profile modificationprocess (e.g., re-shaping) is performed on at least one of the depositedlayers described above with reference to block 106, 108, 110, and/or112. The profile modification process may remove portions of the layerssuch that a modified entry profile is provided for the trench. Theprofile modification process may include a wet etch and/or dry etchprocess. The profile modification process may be performed in a singleetching step. In another embodiment, the modification includes aplurality of steps. In an embodiment, block 114 occurs after theformation of the work function metal layer(s). However, block 114 mayalternatively or additionally occur after any of the deposition stepsdescribed above with reference to blocks 106, 108, and 110, for example,prior to the formation of the next layer in the trench. In oneembodiment, the modification/re-shaping occurs after the dielectric(e.g., HK dielectric) deposition (e.g., prior to the barrier layer). Inone embodiment, the modification/re-shaping occurs after the barrierlayer formation (e.g., prior to the work function layer). In oneembodiment, the modification/re-shaping occurs after the work functionlayer formation.

Referring to the example of FIG. 7, a modified profile opening 702 isillustrated. The modified profile 702 opening is substantially V-shaped.However, other shapes are possible including those described herein.

As illustrated in FIG. 7, the height of at least the layer 602 and 502do not extend to the top of the trench 210 after the modification. Inother embodiments, one or more of each of 302, 402, 502, and 602 may notextend to the top of the trench 210.

As discussed above, the profile modification process may include anetching process or processes. In an embodiment, the etching process is adry etch such as, a plasma etch process. Exemplary processes include,but are not limited to, inductively coupled plasma (ICP), transformercoupled plasma (TCP), electron cyclotron resonance (ECR), reactive ionetch (RIE), and/or other suitable processes. In one embodiment, thereaction gas used in the etching may include BCl₃, Cl₂, HBr, O₂, and/orother suitable etchants. In an embodiment, the profile modificationprocess may include a wet etch process in addition to or in lieu of thedry etch process. The wet etch process may include an etchant such as,for example, NH₄OH, APM (a ammonium hydroxide-hydrogen peroxidemixture), HPM (a hydrochloric acid—hydrogen peroxide-water mixture),and/or other suitable etchants.

The method 100 then proceeds to block 116 where a fill metal is formedin the trench and on the profile modified layers. A fill layer mayinclude Co-Al, Al, W, or Cu and/or other suitable materials. The fillmetal may be formed by CVD, PVD, plating, and/or other suitableprocesses. Referring to the example of FIG. 8, fill metal 802 isdisposed on the substrate 202.

The method 100 then proceeds to block 118 where a planarization processis performed. The planarization process may include a CMP process.Referring to the example of FIG. 9, a planarization process has formed asurface 902.

The planarization forms a gate structure in the trench. The gatestructure is a metal gate structure (e.g., including a metal workfunction layer or metal gate electrode). The gate structure may includean interface layer, a gate dielectric layer(s), a barrier layer(s), awork function layer(s), fill layer(s), and/or other suitable layers.Referring to the example of FIG. 9, a metal gate structure 904 isillustrated. The metal gate structure 904 includes the IL 302, thedielectric 402, the buffer layer 502, the work function metal layer 602,and the fill layer 802.

Embodiments of the method 100 may provide benefits such as improved gapfilling of the fill metal, described above with reference to block 116.For example, in embodiments, the modified profile opening (such as asubstantial V-shape) allows for the fill metal to fill the remainder ofthe trench with the reduction of voiding.

Illustrated in FIG. 10 is a method 1000 of fabricating a semiconductordevice using a replacement gate (also referred to as gate-last)methodology that includes modifying the profile of at least one layer ofa gate structure. The modifying of the profile of at least one layer ofthe gate structure may also be referred to as re-shaping the gatestructure. The modification of the profile or re-shaping provides anopening of the trench within which the gate structure is formed that inembodiments allows for improved gap filling of the trench. This mayprovide a benefit, for example, of avoiding voiding that may form in thereplacement gate structure due to filling difficulties of a high aspectratio trench. FIGS. 2-6 and 11-14 are cross-sectional views of anembodiment of a semiconductor device fabricated according to one or moreof the steps of the method 1000.

It is understood that the method 1000 includes steps having features ofa complementary metal-oxide-semiconductor (CMOS) technology process flowand thus, are only described briefly herein. Additional steps may beperformed before, after, and/or during the method 1000. Similarly, onemay recognize other portions of a device that may benefit from themethods described herein. It is also understood that parts of thesemiconductor devices of FIGS. 2-6 and 11-14 may be fabricated bycomplementary metal-oxide-semiconductor (CMOS) technology process flow,and thus some processes are only briefly described herein. Further,these devices may include various other devices and features, such asadditional transistors, bipolar junction transistors, resistors,capacitors, diodes, fuses, etc., but is simplified for a betterunderstanding of the inventive concepts of the present disclosure. Thesedevices may also include a plurality of semiconductor devices (e.g.,transistors), which may be interconnected. The devices may beintermediate devices fabricated during processing of an integratedcircuit, or portion thereof, that may comprise static random accessmemory (SRAM) and/or other logic circuits, passive components such asresistors, capacitors, and inductors, and active components such asP-channel field effect transistors (PFET), N-channel FET (NFET),metal-oxide semiconductor field effect transistors (MOSFET),complementary metal-oxide semiconductor (CMOS) transistors, bipolartransistors, high voltage transistors, high frequency transistors, othermemory cells, and combinations thereof.

The method 1000 begins at block 1002 where a substrate having a dummygate structure disposed thereon is provided. Block 102 may besubstantially similar to as described above with reference to the method100 of FIG. 1.

The method 1000 then, after subsequent processing typical of areplacement gate process, continues to block 1004 where the dummy gatestructure is removed to provide a trench or opening. Block 1004 may besubstantially similar to block 104 of the method 100, described abovewith reference to FIG. 1. FIG. 2 is illustrative of the substrate 202,the ILD layer 204, the CESL 206, spacer elements 208, and the trench210, as described above.

The method 1000 then continues to block 1006 where an interface layer isformed in the trench. The interface layer may be substantially similarto as described above with reference to block 106 of the method 100 ofFIG. 1. Similarly, FIG. 3 and the illustration of the interface layer302 is exemplary.

The method 1000 then proceeds to block 1008 where a dielectric layer isformed in the trench on the substrate. The dielectric layer (and/or theIL) may provide the gate dielectric for the semiconductor device. Block1008 may be substantially similar to block 108 of the method 100,described above with reference to FIG. 1. Similarly, FIG. 4 and theillustration of dielectric layer 402 is exemplary.

The method 1000 then proceeds to block 1010 where a barrier layer isformed on the substrate including in the trench. Block 1010 may besubstantially similar to block 110 of the method 100, described abovewith reference to FIG. 1. Similarly, FIG. 5 and the illustration ofbarrier layer 502 is exemplary.

The method 1000 then proceeds to block 1012 where a work function metallayer is formed on the substrate including in the trench. Block 1012 maybe substantially similar to block 112 of the method 100, described abovewith reference to FIG. 1. Similarly, FIG. 6 and the illustration of thework function metal layer 602 is exemplary. In an embodiment of themethod 1000, additional layers may be formed in the trench before orafter those discussed above. For example, in one embodiment, anadditional barrier layer is formed after the work function layer(s).

The method 1000 then proceeds to block 1014 where a planarizationprocess is performed. The planarization process may include a CMPprocess. The CMP process may be a metal CMP, for example, removing anexposed metal layer and stopping at an underlying non-metal layer. Inone embodiment, the planarization process removes portions of the workfunction layer. Referring to the example of FIG. 11, a planarizationprocess has been performed resulting in surface 1102. The surface 1102illustrates the removal of the work function layer 602 from the surfaceof the ILD layer. The surface 1102 may include the barrier layer 502. Inan embodiment, the surface 102 includes the dielectric layer 402.

The method 1000 then proceeds to block 1016 where a profile modificationprocess (e.g., re-shaping) is performed on at least one of the depositedlayers described above with reference to block 1006, 1008, 1010, and/or1012. The profile modification process may remove portions of the layerssuch that a modified entry profile opening is provided for the trench.The profile modification process may include a wet etch and/or dry etchprocess. The profile modification process may be performed in a singleetching step. In another embodiment, the modification includes aplurality of steps. In an embodiment, block 1016 occurs after theformation of the work function metal layer(s). However, block 1016 mayalternatively or additionally occur after any of the deposition stepsdescribed above with reference to blocks 1006, 1008, and 1010, forexample, prior to the formation of the next layer in the trench. In oneembodiment, the modification/re-shaping occurs after the dielectric(e.g., HK dielectric) deposition (e.g., prior to the barrier layer). Inone embodiment, the modification/re-shaping occurs after the barrierlayer formation (e.g., prior to the work function layer). In oneembodiment, the modification/re-shaping occurs after the work functionlayer formation.

Referring to the example of FIG. 12, a modified profile opening 1202 isillustrated. The modified profile 1202 is substantially V-shaped.However, other shapes are possible including those described herein.

The height of at least one of the layers 402, 602 and 502 does notextend to the top of the trench 210 after the modification. In otherembodiments, one or more of each of 302, 402, 502, and 602 may notextend to the top of the trench 210.

As discussed above, the profile modification process may include anetching process or processes. In an embodiment, the etching process is adry etch such as, plasma etch processing. Exemplary processes include,but are not limited to, inductively coupled plasma (ICP), transformercoupled plasma (TCP), electron cyclotron resonance (ECR), reactive ionetch (RIE), and/or other suitable processes. In one embodiment, thereaction gas used in the etching may include BCl₃, Cl₂, HBr, O₂, and/orother suitable etchants. In an embodiment, the profile modificationprocess may include a wet etch process in addition to or in lieu of thedry etch process. The wet etch process may include an etchant such as,for example, NH₄OH, APM (a ammonium hydroxide-hydrogen peroxidemixture), HPM (a hydrochloric acid—hydrogen peroxide-water mixture),and/or other suitable etchants.

The method 1000 then proceeds to block 1018 where a fill metal is formedin the trench and on the profile modified layers. A fill layer mayinclude Co-Al, Al, W, or Cu and/or other suitable materials. The fillmetal may be formed by CVD, PVD, plating, and/or other suitableprocesses. Referring to the example of FIG. 13, fill metal 802 isdisposed on the substrate 202.

The method 1000 then proceeds to block 1020 where a planarizationprocess is performed. The planarization process may include a CMPprocess. Referring to the example of FIG. 14, a planarization processhas formed a surface 1402.

The planarization also forms a gate structure in the trench. The gatestructure is a metal gate structure (e.g., including a metal workfunction layer or metal gate electrode). The gate structure may includean interface layer, a gate dielectric layer(s), a barrier layer(s), awork function layer(s), fill layer(s), and/or other suitable layers.Referring to the example of FIG. 14, a metal gate structure 1404 isillustrated. The metal gate structure 1404 includes the interface layer302, the dielectric layer 402, the barrier layer 502, and the workfunction layer 602. However, other embodiments including additionaland/or fewer layers may be possible.

Embodiments of the method 1000 may provide benefits such as improved gapfilling of the fill metal, described above with reference to block 1018.For example, in embodiments, the modified profile opening (such as asubstantial V-shape) allows for the fill metal to fill the remainder ofthe trench without or with the reduction of voiding.

It is noted that the methods described above illustrated a replacementgate or gate-last process that replaced the IL and gate dielectric layeras well as the overlying dummy gate electrode. However, in otherembodiments, the originally formed gate dielectric layer may remain inthe final device. For example, the profile modification or re-shapingmay be performed on a gate dielectric layer formed underlying asacrificial gate electrode (after the gate electrode's removal).

The embodiments described above in FIGS. 7 and 12 illustrate asubstantially V-shaped modification or opening where each layer of thegate structure is etched to provide a substantially co-linear edge (seereference line A). However, other embodiments are possible including,but not limited to those depicted below in FIGS. 15-20.

The devices of FIGS. 15-20 may be formed using the method 100 of FIG. 1and/or the method 1000 of FIG. 10.

FIG. 15 illustrates a device 1500 having a gate structure 1502. The gatestructure 1502 includes an IL 302, a dielectric layer 402, a barrierlayer 502, a work function metal layer 602 and a fill metal layer 802.It is noted that other layers may also be included such as, for example,capping layers, additional barrier layers, and the like. Similarly, oneor more layers may be omitted. One or more of the IL 302, the dielectriclayer 402, the barrier layer 502, the work function metal layer 602 andthe fill metal layer 802 may include a plurality of layers. The heightof the gate structure 1502 is H1. H1 may be depth of the trench formedby the removal of the dummy gate structure. The height of the dielectriclayer 402 is H2. The height of the barrier layer 502 is H3. The heightof the work function metal layer 602 is H3. In the embodiment of thedevice 1500, H1>H2>H3>H4.

The differing heights of the layers of the gate structure 1502 may beprovided by a single etching step (e.g., wet etch, dry etch, plasmaetch, and/or other suitable etching process). For example, the differingetch rate of the materials based on the selectivity of the chosenetching process may provide for differing heights of the layers. Inother embodiments, a plurality of etching steps may be performed. Thediffering heights of the layers of the gate structure 1502 may beprovided by the profile modification process substantially similar to asdiscussed above with reference to block 114 of FIG. 1 and/or block 1016of FIG. 10.

FIG. 16 illustrates a device 1600 having a gate structure 1602. The gatestructure 1602 includes an IL 302, a dielectric layer 402, a barrierlayer 502, a work function metal layer 602 and a fill metal layer 802.It is noted that other layers may also be included such as, for example,capping layers, additional barrier layers, and the like. Similarly, oneor more layers may be omitted. One or more of the IL 302, the dielectriclayer 402, the barrier layer 502, the work function metal layer 602 andthe fill metal layer 802 may include a plurality of layers. The heightof the gate structure 1602 is H1. H1 may be depth of the trench formedby the removal of the dummy gate structure. The height of the dielectriclayer 402 is H2. The height of the barrier layer 502 is H3. The heightof the work function metal layer 602 is H3. In the embodiment of thedevice 1600, H1>H2>H4>H3.

The differing heights of the layers of the gate structure 1602 may beprovided by a single etching step (e.g., wet etch, dry etch, plasmaetch, and/or other suitable etching process). For example, the differingetch rate of the materials based on the selectivity of the chosenetching process may provide for differing heights of the layers. Inother embodiments, a plurality of etching steps may be performed. Thediffering heights of the layers of the gate structure 1602 may beprovided by the profile modification process substantially similar to asdiscussed above with reference to block 114 of FIG. 1 and/or block 1016of FIG. 10.

FIG. 17 illustrates a device 1700 having a gate structure 1702. The gatestructure 1702 includes an IL 302, a dielectric layer 402, a barrierlayer 502, a work function metal layer 602 and a fill metal layer 802.It is noted that other layers may also be included such as, for example,capping layers, additional barrier layers, and the like. Similarly, oneor more layers may be omitted. One or more of the IL 302, the dielectriclayer 402, the barrier layer 502, the work function metal layer 602 andthe fill metal layer 802 may include a plurality of layers. The heightof the gate structure 1702 is H1. H1 may be depth of the trench formedby the removal of the dummy gate structure. The height of the dielectriclayer 402 is H2. The height of the barrier layer 502 is H3. The heightof the work function metal layer 602 is H3. In the embodiment of thedevice 1700, H1>H3>H2>H4.

The differing heights of the layers of the gate structure 1702 may beprovided by a single etching step (e.g., wet etch, dry etch, plasmaetch, and/or other suitable etching process). For example, the differingetch rate of the materials based on the selectivity of the chosenetching process may provide for differing heights of the layers. Inother embodiments, a plurality of etching steps may be performed. Thediffering heights of the layers of the gate structure 1702 may beprovided by the profile modification process substantially similar to asdiscussed above with reference to block 114 of FIG. 1 and/or block 1016of FIG. 10.

FIG. 18 illustrates a device 1800 having a gate structure 1802. The gatestructure 1802 includes an IL 302, a dielectric layer 402, a barrierlayer 502, a work function metal layer 602 and a fill metal layer 802.It is noted that other layers may also be included such as, for example,capping layers, additional barrier layers, and the like. Similarly, oneor more layers may be omitted. One or more of the IL 302, the dielectriclayer 402, the barrier layer 502, the work function metal layer 602 andthe fill metal layer 802 may include a plurality of layers. The heightof the gate structure 1802 is H1. H1 may be depth of the trench formedby the removal of the dummy gate structure. The height of the dielectriclayer 402 is H2. The height of the barrier layer 502 is H3. The heightof the work function metal layer 602 is H3. In the embodiment of thedevice 1800, H1>H3>H4>H2.

The differing heights of the layers of the gate structure 1802 may beprovided by a single etching step (e.g., wet etch, dry etch, plasmaetch, and/or other suitable etching process). For example, the differingetch rate of the materials based on the selectivity of the chosenetching process may provide for differing heights of the layers. Inother embodiments, a plurality of etching steps may be performed. Thediffering heights of the layers of the gate structure 1802 may beprovided by the profile modification process substantially similar to asdiscussed above with reference to block 114 of FIG. 1 and/or block 1016of FIG. 10.

FIG. 19 illustrates a device 1900 having a gate structure 1902. The gatestructure 1902 includes an IL 302, a dielectric layer 402, a barrierlayer 502, a work function metal layer 602 and a fill metal layer 802.It is noted that other layers may also be included such as, for example,capping layers, additional barrier layers, and the like. Similarly, oneor more layers may be omitted. One or more of the IL 302, the dielectriclayer 402, the barrier layer 502, the work function metal layer 602 andthe fill metal layer 802 may include a plurality of layers. The heightof the gate structure 1902 is H1. H1 may be depth of the trench formedby the removal of the dummy gate structure. The height of the dielectriclayer 402 is H2. The height of the barrier layer 502 is H3. The heightof the work function metal layer 602 is H3. In the embodiment of thedevice 1900, H1>H4>H3>H2.

The differing heights of the layers of the gate structure 1902 may beprovided by a single etching step (e.g., wet etch, dry etch, plasmaetch, and/or other suitable etching process). For example, the differingetch rate of the materials based on the selectivity of the chosenetching process may provide for differing heights of the layers. Inother embodiments, a plurality of etching steps may be performed. Thediffering heights of the layers of the gate structure 1902 may beprovided by the profile modification process substantially similar to asdiscussed above with reference to block 114 of FIG. 1 and/or block 1016of FIG. 10.

FIG. 20 illustrates a device 2000 having a gate structure 2002. The gatestructure 2002 includes an IL 302, a dielectric layer 402, a barrierlayer 502, a work function metal layer 602 and a fill metal layer 802.It is noted that other layers may also be included such as, for example,capping layers, additional barrier layers, and the like. Similarly, oneor more layers may be omitted. One or more of the IL 302, the dielectriclayer 402, the barrier layer 502, the work function metal layer 602 andthe fill metal layer 802 may include a plurality of layers. The heightof the gate structure 2002 is H1. H1 may be depth of the trench formedby the removal of the dummy gate structure. The height of the dielectriclayer 402 is H2. The height of the barrier layer 502 is H3. The heightof the work function metal layer 602 is H3. In the embodiment of thedevice 2000, H1>H4>H2>H3.

The differing heights of the layers of the gate structure 2002 may beprovided by a single etching step (e.g., wet etch, dry etch, plasmaetch, and/or other suitable etching process). For example, the differingetch rate of the materials based on the selectivity of the chosenetching process may provide for differing heights of the layers. Inother embodiments, a plurality of etching steps may be performed. Thediffering heights of the layers of the gate structure 2002 may beprovided by the profile modification process substantially similar to asdiscussed above with reference to block 114 of FIG. 1 and/or block 1016of FIG. 10.

In summary, the methods and devices disclosed herein provide for amodified profile gate structure, for example, having one or more layerof the gate stack re-shaped (e.g., decreased in height. In doing so,embodiments of the present disclosure may offer advantages over priorart devices. Advantages of the present disclosure include improved gapfilling of the trench in a replacement gate or gate-last process. It isunderstood that different embodiments disclosed herein offer differentdisclosure, and that they may make various changes, substitutions andalterations herein without departing from the spirit and scope of thepresent disclosure. As but one example, various illustrations providedherein may show a planar transistor. However, one of ordinary skill inthe art would recognize the present disclosure also applies to fin-typefield effect transistor devices (finFET), for example, where the gatestructure is also provided by a replacement gate or gate-last process.

Thus, in an embodiment, described is a method of providing asemiconductor substrate having a trench disposed thereon. A plurality oflayers is formed in the trench. The plurality of layers formed in thetrench is etched, which provides at least one etched layer having a topsurface that lies below a top surface of the trench. In other words, theheight of the etched layer in the trench is less than that of thetrench.

In an embodiment, the etching to form the etched layer includes a dryetch process selected from the group consisting of inductively coupledplasma (ICP), transformer coupled plasma (TCP), electron cyclotronresonance (ECR), and reactive ion etch (RIE) and combinations thereof.

In an embodiment, the plurality of layers in the trench includes a gatedielectric layer and a work function metal layer. In a furtherembodiment, the etching provides a height of the work function layerdisposed in the trench that is less than a height of the gate dielectriclayer disposed in the trench. In another embodiment, the plurality oflayers includes a gate dielectric layer and a work function layer andthe etching process etches at least one of the gate dielectric layer andthe work function layer. In an embodiment, the etching process providesa gate dielectric layer having a first height in the trench and the workfunction layer having a second height in the trench, wherein the secondheight is less than the first height and wherein the first height isdefined by the top surface that lies below the top surface of thetrench.

In an embodiment, after the etching, a fill metal layer is formed in thetrench on the etched layer(s). The etching that layers may includeproviding a substantially V-shaped profile opening in the plurality oflayers.

In another of the methods described herein, a method includes providinga substrate having a dummy gate structure disposed thereon. The dummygate structure is removed to form a trench. A gate dielectric layer onthe substrate and in the trench and a work function metal layer isformed on the gate dielectric layer in the trench. The profile of thegate dielectric layer and the work function metal layer are modified toprovide a substantially v-shaped profile opening on the trench. Thesubstantially v-shaped profile opening is then filled with a fill metal.

In a further embodiment, the work function metal layer is planarizedprior to modifying the profile of the work function metal layer. In anembodiment, the method further includes performing a planarizationprocess after filling the substantially v-shaped profile opening to forma metal gate structure in the trench. The metal gate structure includesthe gate dielectric layer and the work function metal layer.

In an embodiment, the method also includes forming a barrier layer onthe gate dielectric layer and underlying the work function metal layer.The profile of the barrier layer may also be modified concurrently withthe modifying the profile of the gate dielectric layer and the workfunction metal layer.

Modifying the profile includes at least one process of: inductivelycoupled plasma (ICP), transformer coupled plasma (TCP), electroncyclotron resonance (ECR), and reactive ion etch (RIE).

Also described herein is a semiconductor device having a semiconductorsubstrate with a dielectric layer disposed thereon. A trench is definedin the dielectric layer. A metal gate structure is disposed in thetrench. The metal gate structure includes a first layer and a secondlayer disposed on the first layer. The first layer extends to a firstheight in the trench and the second layer extends to a second height inthe trench; the second height is less than the first height.

In an embodiment of the device, the first layer is a gate dielectriclayer and the second layer is a metal work function layer. In anembodiment, the metal gate structure further includes a third layerdisposed on the second layer. The third layer extends to a third heightless than the second height. In a further embodiment, the third layer isa work function metal layer, the second layer is a barrier layer and thefirst layer is a gate dielectric layer. In an embodiment of the device,the metal gate structure further includes a fill metal layer. The fillmetal layer has an interface with the first layer and the second layer.

What is claimed is:
 1. A semiconductor device, comprising: asemiconductor substrate having a top surface; and a gate structuredisposed over the semiconductor substrate, wherein the gate structureincludes: a first layer of a substantially U-shaped configuration andextending to a first height above the top surface; a second layer havinga substantially U-shaped configuration and extending to a second heightabove the top surface; a third layer having a substantially U-shapedconfiguration and extending to a third height above the top surface,wherein the first height, the second height and third height aredifferent; and a fill layer disposed over the first, second and thirdlayers wherein a top surface of the fill layer is disposed at a fourthheight from the top surface of the semiconductor substrate, wherein thefourth height is greater than the first, second and third heights,wherein the second height is greater than the first height.
 2. Thesemiconductor device of claim 1, wherein the gate structure furtherincludes an interfacial layer underlying the first layer.
 3. Thesemiconductor device of claim 1, wherein the second layer is TaN.
 4. Thesemiconductor device of claim 1, wherein the third layer is a metallayer.
 5. The semiconductor device of claim 1, wherein the first layeris a high-k gate dielectric layer.
 6. The semiconductor device of claim1, wherein the third height is greater than the second height.
 7. Thesemiconductor device of claim 1, wherein the third height is greaterthan the second height.
 8. A semiconductor device comprising: a gatestructure disposed on a semiconductor substrate, the gate structurehaving: a gate dielectric layer having a bottom portion and two sideportions extending vertically above the bottom portion to a first heightfrom a surface of the semiconductor substrate; a metal layer over thegate dielectric layer and having a bottom portion and a first sideportion and a second side portion each extending vertically above thebottom portion of the metal layer to a second height from the surface ofthe semiconductor substrate, wherein the first side portion of the metallayer is defined by a first sidewall and a second sidewall opposing thefirst sidewall and the second side portion of the metal layer is definedby a third sidewall and a fourth sidewall opposing the third sidewall;and a fill metal layer disposed over the metal layer and interfacingboth the first sidewall, the second sidewall, the third sidewall and thefourth sidewall of the metal layer and interfacing a top surface of eachof the two side portions of the gate dielectric layer.
 9. The device ofclaim 8, wherein the second height is greater than the first height. 10.The device of claim 8, wherein the metal layer is a TaN layer.
 11. Thedevice of claim 8, further comprising: a TaN layer interposing the metallayer and the gate dielectric layer, wherein the TaN layer has a thirdheight extending from the surface of the semiconductor substrate, thethird height different from the first height.
 12. The device of claim11, wherein the third height is greater than the second height.
 13. Thedevice of claim 12, wherein the first height is less than at least oneof the second height and the third height.
 14. The device of claim 8,wherein the fill metal layer is cobalt.
 15. The device of claim 8,wherein the fill metal layer is tungsten.
 16. A semiconductor devicecomprising: a gate structure disposed on a semiconductor substrate, thegate structure having: a gate dielectric layer having a bottom portionand two side portions extending vertically above the bottom portion to afirst height from a surface of the semiconductor substrate; a firstlayer over the gate dielectric layer and the first layer having a bottomportion and two side portions each of the two side portions havingrespectively a first sidewall and a second sidewall extending verticallyabove the bottom portion to a respective first top surface disposed asecond height from the surface of the semiconductor substrate, whereinthe first layer includes a first metal; a second layer over the firstlayer, the second layer having a bottom portion and two side portionseach of the two side portions having respectively a third sidewall and afourth sidewall extending vertically above the bottom portion to asecond top surface disposed a third height from the surface of thesemiconductor substrate, wherein the third height is different than thesecond height, wherein the second layer includes a second metal; and afill metal layer comprising a first composition disposed over the firstlayer and the second layer, wherein the first composition interfaces thefirst top surface, the second top surface, and at least one of the firstand second sidewalls of the first layer or the third and fourthsidewalls of the second layer.
 17. The device of claim 16, wherein thefirst metal is Ti and the second metal is Ta, and the first compositionis tungsten (W).
 18. The device of claim 17, wherein the first layer isTiN and the second layer is TaN.
 19. The device of claim 16, wherein thefirst composition of the fill metal layer interfaces the first sidewalland the second sidewall of the first layer.
 20. The device of claim 16,wherein the first height is different than each of the second and thirdheights.